Development in mammals involves the modulation of gene expression during cell differentiation. We are investigating two sets of genes active during mouse pre-implantation development. One set contains homeobox sequences which have been shown to control spatial relations in Drosophilia development. We have recently indentified clones from a mouse cDNA overian library which cross-hybridize with Drosophilia homeobox probes and are determining if these mouse genes contain homologous homeobox sequences. The second set of genes we study code for the three sulfated glycoproteins of the mouse zona pellucida (ZP-1, ZP-2 and ZP-3). The products of this gene family are germ-line specific and active only during meiosis where their coordinate regulation occurs in the absence of cell division. We have developed monoclonal antibodies which are specific for ZP-2 and ZP-3. Using these immunological probes we have isolated cDNA clones coding for ZP-3 from a ovarian cDNA library in the Lambdagtll expression vector. ZP-3 message is expressed as a 1.7 kb polyadenylated mRNA which is found exclusively in ovarian tissue. Southern blot analyses of restriction enzyme digests of DNA from brain, liver and ovary reveal similar genomic organization of ZP-3, although there is hypomethylation of the ZP-3 locus in ovarian tissue. Mouse ZP-3 cDNA cross-hybridizes with DNA from a wide variety of mammals including rat, rabbbit, dog, pig, cow and human. Parenteral administration of anti-zona monoclonal anitbody results in antibody localization to the ovary where it coats growing oocytes. Although ZP-3 is thought to be the species-specific sperm receptor, monoclonal antibodies to either ZP-3 or ZP-2 appear equally effective in inhibiting in vitro and in vivo fertilization. The contraceptive effect is long-term but totally reversible and the presence of the monoclonal antibodies had no adverse affect on early development. These observations couples with our ability to express recombinant ZP-3 as fusion proteins will allow us to test the efficacy of a contraceptive vaccine based on the zona proteins.